To round a floating-point number in Go, you can use the math.Round() function from the built-in math package. However, this function rounds to the nearest integer, so it cannot be used directly to round a float to a particular precision. But you can use it to create your own function that rounds to any decimal places. All you need to do is:
- multiply the number to be rounded times 10 to the power of
X, whereXis the precision you want to achieve - round this raised number to the nearest integer value using the
math.Round()function - divide the rounded number by 10 to the power of
X, whereXis the rounding decimal precision
In this way, by rounding the raised number to the nearest integer and then dividing, we get a number rounded to the specified decimal places.
Examples
The roundFloat() is a floating-point rounding function, working as described above. The way it works is shown in the example:
package main
import (
"fmt"
"math"
)
func roundFloat(val float64, precision uint) float64 {
ratio := math.Pow(10, float64(precision))
return math.Round(val*ratio) / ratio
}
func main() {
number := 12.3456789
fmt.Println(roundFloat(number, 2))
fmt.Println(roundFloat(number, 3))
fmt.Println(roundFloat(number, 4))
fmt.Println(roundFloat(number, 5))
number = -12.3456789
fmt.Println(roundFloat(number, 0))
fmt.Println(roundFloat(number, 1))
fmt.Println(roundFloat(number, 10))
}
Output:
12.35
12.346
12.3457
12.34568
-12
-12.3
-12.3456789
Round float to 2 decimal places
Full example of rounding a float to 2 decimal places:
package main
import (
"fmt"
"math"
)
func roundFloat(val float64, precision uint) float64 {
ratio := math.Pow(10, float64(precision))
return math.Round(val*ratio) / ratio
}
func main() {
number := 12.3456789
fmt.Println(roundFloat(number, 2))
}
Output:
12.35
Round float to 3 decimal places
Full example of rounding a float to 3 decimal places:
package main
import (
"fmt"
"math"
)
func roundFloat(val float64, precision uint) float64 {
ratio := math.Pow(10, float64(precision))
return math.Round(val*ratio) / ratio
}
func main() {
number := 12.3456789
fmt.Println(roundFloat(number, 3))
}
Output:
12.346